Pneumatic switch



March 30, 1948. J. MEHUT PNEUMATIC SWITCH Filed March 1, 1945 INVENTOR .Z /i/Y M51911 7' Patented Mar. 30, 1948 PNEUMATIC SWITCH Jean Mehut, Lyon, France, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application March 1, 1943, Serial No. 477,652 In France February 21, 1942 Section 1, Public Law, 690, August 8, 1946 Patent expires February 21, 1962 2 Claims. (Cl. 200-83) The present invention relates to a fire alarm system and to a pneumatic relay for use in such system.

More specifically, the invention relates primarily, though not exclusively, to a fire alarm system with pyrotechnical detectors, i. e. detectors which operate when a powder charge contained therein is heated beyond a predetermined temperature to transmit the sudden increase in pressure caused by the combustion of said charge through suitaable conduits to an alarm or indicator device, and, if desired, to a mechanism for releasing a sprinkler mechanism at the point where the detector has been excited.

In fire alarm systems of this type, it is highly desirable to shorten the pneumatic conduits lead" ing to the indicator device or to the sprinkler mechanism, because the powder charges used in the detectors of such alarm systems are subject to a gradual decrease of their power of expansion upon aging, and when the pneumatic conduits are too long, it may happen that the pressure wave produced by the excitation of a detector containing a more or less stale charge fails to develop sufiicient power for the actuation of the alarm or the sprinkler. On the other hand, for certain purposes, and especially if the alarm device is to be located on a switchboard carrying electrical elements, it is desirable to insure the homogeneousness of the switchboard by the provision of electrical control means for the alarm device.

Consequently, it is one object of the present invention to provide a fire alarm system of the type mentioned, in which the pneumatic conduits are extremely short.

Another object of the invention is to provide a fire alarm system with pyrotechnical detectors in which the mechanisms controlled by the detec tors, such as the alarm device and the sprinkler are operated by means of an electric current.

Still another object of the invention is to provide a pneumatic-electrical relay which is capable of converting pneumatic energy rapidly and safe- 1y into electric energy, e. g. for the control of the alarm devices and sprinklers in a fire alarm system.

These and other objects are accomplished, according to the present invention, by the arrangement and combination of parts set forth in the following description, defined in the appended claims and illustratively exemplified in the accompanying drawing, in which Fig. 1 is a diagram of a pyrotechnical fire alarm system of known type;

Fig. 2 is a similar diagram of a pyrotechnical fire alarm system according to the present invention;

Fig. 3 is an elevational view of a pneumaticelectrical relay suitable for use in a fire alarm system according to Fig, 2, the protective cover being removed to show the contact arrangement; and

Fig. a is a sectional View of this relay taken on line A-B of Fig. 3.

Referring to the drawing and particularly to Fig. 1, the fire alarm system shown in the diagram comprises a number of pyrotechnical detectors I, I arranged at suitable points of the premises or installations to be protected and connected by individual pneumatic conduits 2, 2 to one end of a common pneumatic conduit 3. The other end of the common conduit 3 is connected to two branch conduits 4 and 5, the branch conduit 4 leading to a device 6 producing a visual or audible signal, and the branch conduit 5 terminating in a sprinkler control device 1.

Experience has shown that pyrotechnical detectors of the type in question are rather unreliable because, after a certain time, the powder charge is subject to a chemical deterioration. Consequently, the pressures transmitted by the operation of the detectors into the conduits I, l, 2, 2, 3, 4 and 5 are of variable magnitude, and the energies transmitted through the long pneumatic conduits may become insufficient to cause the operation of the alarm device and of the sprinkler or of either one of them. This disadvantage of a fire alarm system of the type described is eliminated according to the invention by an arrangement, as shown diagrammatically in Fig. 2, including means disposed close to the detectors 1, I for transforming the pneumatic energy received from the detectors into electrical energy. As shown in Fig. 2, the device accomplishing this transformation is a relay 8 disposed at the beginning of the common conduit 3. The alarm device 6 and the sprinkler 1' are, in this case, designed in a manner well known. in the art to be electrically activated by the application or cessation of a current from the battery 9 controlled by the relay 8 in response to the pressure wave arriving at said relay 8 through the conduit 3 when one of the detectors 1 I is excited.

The relay which serves for the conversion of the pneumatic energy into electrical energy may be constructed in any desired manner with pneurgnatically actuated dry contacts or mercury conac s.

Figs. 3 and 4 illustrate a preferred embodiment of a converter relay suitable for this and other purposes.

In these figured, I denotes the body of the relay, said body being provided with a screw threaded recess II to receive the end of the pneumatic conduit 3. From the recess I I, a pas;-

sage I 2 leads to a gas expansion chamber I3- having its bottom and side walls formed by thev body I9 itself. The top wall of the chamber I3 is formed by a rubber diaphragm I4, clamped alon its circumference between the body It); and a dome-shaped cover I5 secured to the body It by means of screws I'Ea, so as to make the chamber I3 completely tight. Centrally on the. outer face of the diaphragm I 4, rests a pushbutton having a flat portion I6, the large surface of which contacts the diaphragm I 4, and a piston I'I freely displaceable in a guide sleeve mounted in the apex of the cover I5. The piston I I is provided with a needlepoint I3.

When an increase of pressure occurs in the cylindrical chamber iii, the diaphragm I4 is deformed and takes along the push button I5, I! displacing the same along the axis of the guide sleeve in the cover I5.- A switch base 24 is seeured to the cover l5, and carries at one end thereof a fixed contact 25. A conductor spring blade I9 is mounted on the other raised end 0d the base 24 by means of a screw 2i. The spring blade I9 extends parallel to the base 24 and carries on its free end, opposite the fixed contact 25, a movable contact 29. A pressure plate 22 with an inwardly bent portion is mounted on top of the spring blade. I9; and holds the latter normally in the position shown in the drawing. When, upon transmission of a pressure wave to the chamber I3, the diaphragm I4 is deformed and the needle point I8 knocks against the portion of the spring blade I9 at the end of the pressure plate 22, the blade i9 is abruptly deformed and the contact 20, 25 is instantaneously broken,

Reversely, when the needle point I8 ceases to actupon the spring blade I9, upon a reduction of the pressure. in the chamber I3, the spring blade I9 returns instantaneously to its normal position. The time required for a reduction of the pressure in thechamber I3 is very brief, because the overpressure produced in said chamber is rapidly dissipated through the leak passage 23.

ihus opening and closing of the circuit controlled by the relay takes place freely and abruptly and any burning of the contacts due to 4 self-induction ofthe circuit is positively avoided. It will be understood that the invention is not limited to the embodiment shown and described but is capable of numerous variations and modifications within the scope of the following claims.

I claim:

,1. A pneumatic-electrical relay for the conversion of a rapid pulse of pneumatic energy to a, corresponding rapid pulse of electrical energy, said relay including a body formed with a chamber open on one side thereof, a flexible diaphragmpof rubber like material secured to said body so as to close the open side of said chamber, means to connect said chamber with a source or rapidly pulsing pneumatic energy, a push button having a radial enlargement providing a substantially fiat surface resting on the outer face of said diaphragm, a switch base mounted on said body and carrying a fixed Contact element and a movable contact element, said movable contact element including a spring blade disposed in the path of said push button and deformable by the latter to open its normally closed contact, a dome shaped cover member inserted between said body and said switch base and provided with a guide sleeve to receive the push button and-said push buttcn beingprovided at its outer end with a contact element engaging portion radially eniarged to engage the sleeve end to limit inward movement of the push button.

2. A pneumatic-electrical relay as claimed in claim 1 wherein the body is formed with a bleeder opening to the exterior.

JEAN MEHUT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 11,471 Ludlow Feb. 12, 1895 2,027,068 Siddall et al. Jan. 7, 1936 1,869,204 Lowe et a1 July 26, 1932 2,168,244 Rouse Aug. 1, 1939 1,849,481 De Langie et al. Mar. 15, 1939- 1,934,894 Valentine Nov. 14, 1933 1,174,149 Hirnrner Mar. 7, 1916 1,951,245 Jardine Mar. 13, 1934 2,136,504 Hilbert et al. Nov. 15, 1938 1,232,456 Bliss July 3, 1917 2,117,213 Rodanet May 10, 1938 2,260,636 Neif Oct. 28, 19.41 

